1. Field of the Invention
This invention relates to an improved process for synthesizing bisphthalonitrile derivatives having imide and ester-imide linkages, and to a process for preparing phthalocyanine polymers from those derivatives. More particularly, it relates to such processes which result in phthalocyanine polymers having increased thermal and thermo-oxidative stability and toughness over prior art phthalocyanine polymers.
2. Description of the Prior Art
Polymers incorporating a phthalocyanine structure in the polymeric backbone have been of considerable interest in the prior art, due to hoped for properties to be obtained with such polymers, such as thermal stability, chemical inertness, pleasing color, semiconductivity, catalytic activity and photoconductivity. In particular, it is felt that the incorporation of the phthalocyanine structure should increase the heat resistance property of polymers, as well as giving increased fire resistance and resistance to moisture absorption. However, many attempts in the prior art to prepare such phthalocyanine polymers fail to give phthalocyanine polymers with high molecular weight. More recently, the successful synthesis of many ether- and amide-linked bisphthalonitrile derivatives and their polymerization has resulted in phthalocyanine polymers having high degrees of polymerization. Such derivatives and their polymers are described in, for example, U.S. Pat. No. 4,234,712, issued 1980 to Keller et al.; U.S. Pat. No. 4,067,860, issued Jan. 10, 1978 to Griffith et al.; U.S. Pat. No. 3,993,631, issued Nov. 23, 1976 to Griffith et al.; and by Walton et al., Polym. Sci. Technol. Adhes. Sci. Technol., 9B, 665 (1975). These polymers can be heat cured alone or in the presence of a metallic salt or powder.
The polymerization of ether-linked bisphthalonitrile derivatives has also been studied in the presence of hydrogen donating curing agents such as benzyl trimethyl ammonium hydroxide, hydroquinone, catechol, resorcinol, benzoin, bisphenol A, and the like, in order to decrease polymerization time, as reported by Marullo et al., Polym. Prepr., Am. Chem. Soc. Div. Polym. Chem., 22, 48 (1981).
Although the polymers resulting from such work had some increased thermal stability, they appear to be somewhat less stable than hoped for in a polymer having a phthalocyanine structure.
Polyimide-metallophthalocyanines are also known, as described in, for example, U.S. Pat. No. 3,890,274, issued June 17, 1975 and U.S. Pat. No. 3,996,196, issued Dec. 7, 1976 to D'Alelio. These polymers are made by synthesizing a bisphthalonitrile using a bisphthalic anhydride derivative, an aromatic diamine and an aromatic compound containing two orthocyano groups and one amino group. Polymerization is then effected by heat alone, or in the present of metal salts or powders. However, this method of preparing the bisphthalonitrile compounds appears to involve side reactions, in addition to producing non-uniform bisphthalonitrile derivatives, therefore apparently adversely affecting the properties of the polymers produced. Further, D'Alelio describes a phthalocyanine structure wherein the "n" is a positive integer of at least one. There is no method described such that "n" is always zero for the four "G" groups attached to the pthalocyanine structure. Therefore, regular uniform sheet-type or ladder-type phthalocyanine polymers are not possible to be formed from these monomers and this approach.
A wide variety of polyimides are also known in the prior art. U.S. Pat. No. 3,897,395, issued July 29, 1975, and U.S. Pat. No. 4,060,515, issued Nov. 29, 1977, both to D'Alelio, disclose nitrile terminated polyimides prepared by reacting an aromatic dianhydride with an aromatic diamine and, optionally, an organic monoamine. U.S. Pat. No. 3,948,941, issued Apr. 6, 1976, to Patton, discloses a process for the preparation of polyimides using isocyanates and a catalytic quantity of a cyanide ion. U.S. Pat. No. 4,021,415, issued May 3, 1977, to Chang teaches nitrile containing polyamides. U.S. Pat. No. 4,069,209, issued Jan. 17, 1978 to Lange discloses imino acid resins and poly(ester-imides) prepared from such resins. U.S. Pat. No. 4,368,319, issued Jan. 11, 1983 to Hocker et al., discloses film forming electrically conductive cyclic polyimides, prepared from reacting a dianhydride with various alkylene amines.
U.S. Pat. No. 4,238,601, issued Dec. 9, 1980 to Keller et al. also discloses the preparation of phthalocyanine polymers from bisorthonitrile monomers.
Thus, while the art pertaining to polyimides, polyester-imides and various phthalocyanine polymers is a well developed one, a need remains for the preparation of phthalocyanine polymers which achieve more of the potential value of incorporating phthalocyanine moieties in a polymeric backbone.